Underwater search for lost Malaysia Airlines Flight 370 will resume by the end of this month after work finishes on a ship enlisted to scan the ocean floor.
Two ships, Malaysia’s GO Phoenix, now undergoing the work, and another vessel provided by Dutch company Fugro, will focus on an area further south than initially planned.
The two vessels will use towed side scan sonars to examine the bottom of the ocean from only 90 metres above. The work is expected to be particularly challenging as the sea floor is believed to lie in depths of almost 6km in some places.
The data from the "towfish" will be transmitted in real-time back to the crew aboard the ships, who will look for any signs of unusual debris. The search is expected to take up to a year.
The priority zone has been shifted southwards after a revision of automated data transmissions between the aircraft’s systems and satellites persuaded officials the aircraft may have turned south earlier than previously thought.
The GO Phoenix will begin its search on 30 September in the southerly stretch of ocean, located along what is known as the "seventh arc" - a 23,000 square mile targeted area where investigators believe the plane ran out of fuel and crashed, based on the last ping from the engine transmitters.
"Our plan has a sequence of priorities," said Australian transport safety bureau chief commissioner Martin Dolan. "It's all about probability - we'll start with the highest probability."
The second ship, provided by Dutch contractor Fugro Survey, will probably focus on an area south of the GO Phoenix when it eventually arrives, he said.
Flight 370 disappeared on 8 March this year after veering off its northerly course from Kuala Lumpur to Beijing for unknown reasons.
It is thought to have crashed 1,100 miles off Australia's west coast. No trace of the aircraft or the 239 people on board have been found during months of desperate search efforts.